Motion artifact is a significant source of noise in ambulatory ECG recordings, EEG recordings, and other recordings that rely on skin surface electrodes. Present methods for motion artifact reduction require time consuming preparation and patient discomfort and are not always effective. We will investigate the use of skin impedance or skin stretch measurements in conjunction with adaptive noise removal to reduce motion artifact in ECG recordings without skin abrasion and the associated preparation and patient discomfort. We have previously used stretch sensor signals to remove motion artifact from ECGs when we generated the motion artifact in a controlled setting. In this study we will extend our previous work to ambulatory recordings and compare the performance of motion artifact removal based on skin stretch sensors to the more economical approach of using skin impedance to adaptively remove motion artifact. Reliable removal of motion artifact will improve the performance of any monitoring or diagnostic system that relies on skin surface electrodes. PROPOSED COMMERCIAL APPLICATIONS: This technology has the potential to be applied to all ambulatory BCG recording (Holter) systems, stress test systems, event recording systems, and patient monitoring systems. There are an enormous number of these systems in use, so any system which can significantly reduce the motion artifact inherent in these recording systems has tremendous commercial potential.